When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
CLK320, will not crank and the fan runs at full speed. Replaced the k40 relay box with a genuine merc part. Touched a couple of the pins and the motor cranked so figure it is not a starter motor issue. Can't hear the fuel pump go. Possibly unrelated is that the temp and gear LCD on the dashbaord are pixilated, i.e. not reporting correctly. Have a hunch the ECU may not be getting power or the ECU has failed. Previous owner said that a wire to the fuel pump was replaced, which makes no sense, but can't get greater clarity. Any suggestions? How could I test to see if the ECU gets power?
Additional info: When I cranked the engine (by connecting the two pins) for a quite a few seconds the fan stopped. I am guessing the ECU detected engine movement via the crank position sensor and sent that message to the fan - does the CPS report direct to the ECU or does it also report to some other electronic bit which then activates the fan?
Hi All, as this is a very old thread, I thought it might still be interesting because just had this issue.
With thanks to all who have replied to this before, Suspecting Temperature sensor and ECU goes way too far.
I had the exact same symptoms on my 2004 W209 with M112 (240) . All light come on when turning the key (except Water Temperature which remains 0 or blank) and few seconds later the Radiator Fan goes on full speed.
It turned out to be from the start enable relay (I read here that someone called it K40). It is one of the black relays on the front SAM. Marked with Red Cross in my photo.
I opened the casing of the relay and pushed it by hand and Voila everything worked.
Just to make sure I swapped the two black relays and the symptoms changed. So, that was our bad guy.
Hope it helps
.
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren
Slideshow: A one-of-one U.S.-spec Mercedes-Benz SLR McLaren Roadster became even rarer after a factory-backed transformation at McLaren's headquarters.
